James Turner wrote:
> On 3 Oct 2008, at 13:15, Heiko Schulz wrote:
>> I agree to nearly all what you said, but why not release an official
>> 2.0-pre-version with OSG which shows to the world that we are still
>> alive? Maybe as an advertisement to other developers?
> Yep, that's what I said :)
I think that's a great idea too. As Matthew Tippet said in his email a few days
ago, the multi-channel support in CVS is pretty unique and would be nice to show
off. Among all the other features...
>> In the moment I see that the clouds and shadows are a "one-man-
>> project"- so now wonder that it needs a long time until we will have
>> these features back.
>> I wonder if it really needs so much knowledge about OSG, and if
>> other developers could help here?
I don't much like being the graphics critical path and I've tried to help /
mentor others who have wanted to contribute to the graphics code. To date these
contributions have come from people other than Mathias and myself (sorry if I'm
leaving anything out):
* random objects
* fast trees (forests really)
* Good support of OSG particle systems
* precipitation effects
* scenery paging and model loading improvements
I hope that the folks that did that work will report that they were supported in
Working with OSG does require basic knowledge of computer graphics, OpenGL and
C++, but otherwise it is not mysterious. So if anyone wants to pitch in, please do.
> Well I just read over Stuart's code, with a view to doing exactly
> that. It's a part of the code I am completely unfamiliar with,
> however, so I need to do a lot more reading before I can make any
> intelligent comments about it, let alone try and fix it.
Stuart has run into a bug in OSG with respect to Imposters, which manage the
cached rendering of the individual cloud sprites. It's unclear if this ever
worked well in OSG. Unfortunately I haven't had the chance to really look at the
> I don't suppose anyone has the link to the 'original' cloud code,
> before it was ported to PLIB, or the technical description? Or perhaps
> there's a doc link the cloud code itself, I'll keep digging.
I think this code is "original." At one point Mark Harris' clouds were in the
tree, but they proved to be to expensive for the machines of the day, AIUI; the
current code is a simplification of that.
> Incidentally, on the shadows, I always assumed that's something we
> would get 'for free' with OSG, presumably there is some technical
> obstacle to just enabling one of the OSG shadowing techniques? I can
> believe that some of them are impractical for FG, but equally we only
> have on light source (that matters for shadowing) most of the time -
> floodlit airfield and carrier operations excepted. Could someone
> enlightened (Tim, I guess) explain the outstanding issues in that area?
The problem is that our vast scene overwhelms most shadowing techniques. When I
turned my attention to this subject I decided not to use the "shadow volumes"
technique used in plib. This is CPU-expensive and has a lot of special cases
that don't work well. The alternative is shadow maps, and there are several
implementations in OSG. The only ones that have a chance of working well are
Parallel Split Shadow Maps (PSSM) and a new addition, View Dependent Shadow
Maps. The former has always been complicated and buggy. OSG users are excited
about the latter, which warps the shadow map based on the extents of the scene,
and I have been working on getting it going with fg. Unfortunately, very few
(perhaps no) people use these techniques with geocentric databases. I'm
currently working through a large bug that I believe is related to that.
Just to say it again: if anyone wants to help with the graphics code, please
jump in. I can't teach basic graphics programming, but I am available on IRC a
lot to help with OSG questions.